Effect of Nitrogen Doping and Oxidation of Graphene on the Deposition of Platinum from Trimethyl(methylcyclopentadienyl)platinum(IV)

Abstract

Materials composed of nitrogen-doped carbon are useful as catalyst supports due to their low cost, low density, and enhanced metal–support interaction. One way to synthesize catalytic single atoms and nuclei on these supports is via vapor phase deposition processes. Here, density functional theory (DFT) was used to evaluate the effects of N doping and oxidation of graphene on the adsorption and dissociation of trimethyl­(methylcyclopentadienyl) platinum (MeCpPtMe3), which is a commonly used precursor in vapor deposition of platinum. DFT calculations confirmed that oxygen incorporation into graphene via oxidation of vacancies is thermodynamically favorable with and without N dopants. N doping was found to elongate substrate–oxygen bonds, thereby enhancing the interaction between MeCpPtMe3 and oxidized defective graphene. According to nudged elastic band calculations, MeCpPtMe3 dissociation on all oxidized substrates, with or without N doping, displayed positive enthalpies of reaction and activation energies. However, N doping drives the reactions by lowering the enthalpy of reaction and activation energy for the dissociation of MeCpPtMe3 and the enthalpy of reaction for the subsequent chemisorption of MeCpPtMe2, which was exothermic in all cases. Finally, the entire reaction beginning with MeCpPtMe3 and two unreacted oxidized monovacancies and ending with MeCpPtMe2 and a methyl group each bound to an oxidized monovacancy is exothermic for substrates containing pyridinic-N dopants.